The foundations of
church law on marriage were laid during the eleventh
and twelfth centuries, the period of the Gregorian Reforms. These can
be
summarized briefly:

With regard to marriage and divorce, the legislation of the
eleventh and
twelfth centuries implanted firmly the doctrine of marital
indissolubility;
the only permissible grounds for divorce and remarriage were impotence,
incest (i.e., marriage within the forbidden degrees of consanguinity
and
affinity), and adultery. This threatened to end the widespread practice
of divorce; it also encouraged the church to assert its judicial
authority
over marriage law; and it diminished the ability of family and kin to
control
marriage independently.

With respect to incest, the forbiddendegrees
of consanguinity
and affinity remained high. In 1059, Pope Nicholas II issued an
encyclical
which required that "if anyone had taken a spouse within the seventh
degree,
he will be forced canonically by his bishop to send her away; if he
refuses,
he will be excommunicated." In 1215, the Fourth Lateran
Council reduced the number of prohibited degrees from seven to
four.
Still, the cummulative effect was to encourage exogamy--i.e.,
marriage
outside one's native community--and the growth of regional marriage
markets.

The reforms codified a trend toward monogamy,
already well under
way by the turn of the millenium, which supplanted earlier forms of
polygynous
marriage and concubinage, such as Friedelehen (a kind of
second-class
marriage).

The canonists also asserted authority over the sexual
practices of laypeople:
the reform-era legislation was generally milder than earlier
regulations,
but continued to uphold the notion that sex for any purpose other than
procreation within marriage was sinful. All nonmarital sex was
condemned
as criminal; all homosexual intercourse was forbidden.

It
is unclear how consistently the provisions on forbidden degrees of
incest
were enforced; considerable controversy centered on the reckoning of
degrees
of kinship, for which there were two systems in operation, the Roman
and
the far stricter Germanic scheme. Under the Roman scheme, degrees of
kinship
were calculated by counting the number of acts of generation separating
ego and other. Siblings, under this system, were separated by two
degrees
of kinship, one for the act of generation between the first sibling
from
her parents, another for the act of generation between the parents and
the second child. Similarly, an uncle and niece are separated in the
third
degree.

Image right:
the "Germanic" system for calculating degrees
of separation, adapted from Isidore of Seville (Etymologarium sive
Originum,
ed. W.M. Lindsay, Oxford, 1911); in Jack Goody, The Development of
the
Family and Marriage in Europe (Cambridge: Cambridge University
Press,
1983), 143.

According to the Germanic
calculation, degrees of kinship were based
on the unity of the sibling group, all of whom were related in the
first
degree, so that all brothers and sisters of a single marital couple
were
related to each other in the first degree. By this system of reckoning
from a hypothetical "ego" (ipse on the chart), seven degrees of
separation included all descendents from a pair of common
great-great-great-great-great-grandparents.
Under this system, the circle of kinship embraced all descendants of a
common great-grandfather, i.e., second-cousins.

Moreover, these provisions
left open the question of how a marriage
came into being. This matter was given much sharper definition in
Gratian's
Decretum
(ca. 1140). Gratian tended to regard marriage as a process with two
stages:
(a) in
initiation, the couple exchanged freely-consenting vows of
marriage, which created a spiritual union between them; in the (b) completion
or
perfection of the marriage, the couple created a physical union
by consummating their bond sexually. Both stages were necessary to
complete
a marriage: no sexual union constituted marriage without consent to
marry,
just as no marriage as wholly formed without sexual union. Indeed, for
Gratian it was sexual intercourse that transformed the union into a
"sacrament"
and made a marriage indissoluable. If marriage was situated between
three
kinds of union -- sexual, spiritual, and social -- Gratian's
Decretum
shifted definitions strongly toward the first of these. But not to the
neglect of consent: only a marriage freely entered was valid, if both
parties
were at least seven years old, both were Christian, and neither were
bound
by an oath of chastity.

With its emphases on the
necessity of consent
and on sex as a positive good, the High Medieval conceptualization of
marriage
represented a departure from the hostility and revulsion toward
sexuality
that characterized the writings of many earlier canonists. As it
developed
after Gratian, canon law also distinguished between two kinds of vows,
and weighed them differently depending on whether these vows had been
consummated
sexually.

1. “Present Vows” (sponsalia
per verba de praesenti)
Present vows were an exchange of promises in the present, for the
present,
between consenting male and female (i.e., "I, Margot, take you, Hannes,
to be my husband now and forever"). In general, these were thought to
constitute
a valid marriage, even if the vows were exchanged in secret and without
the consent of parents and kin.

If present vows were consummated, i.e, if they were sealed spiritually
through sex, they constituted a valid marriage and were therefore
indissoluble.

If present vows were left unconsummated, the union could still be
dissolved
only
if

(a) one of the two parties entered a monastery (i.e., took a higher
vow);
or

(b) the pope granted a dispensation from the requirements of canon law.

2. “Future Vows” (sponsalia
per verba de futuro)Slightly more complicated
were future vows of marriage exchanged between
consenting parties (i.e., "I, Margot, promise to take you, Hannes, to
be
my husband at such-and-such a date"). Future vows were obligating, but
did not constitute an indissoluable marriage for the present. Therefore
future vows could be dissolved

By mutual consent of the parties involved; or

If one of the two made present vows with somebody else (i.e.,
took
a higher vow); or

If one of the two moved to a foreign land; or

If one of the two had heterosexual intercourse with somebody else; or

If one of the two became a heretic or an apostate; or

If one of the two became a leper.

In this system, the
social dimension of marriage got short shrift: Gratian
was no enthusiast for clandestine marriage, but his emphasis on consent
and sexual consummation left little room for parental consent or the
need
for public, ceremonial marriage. Indeed, the emphasis on consent in
marriage
only grew stronger: Pope Alexander III (1159-1181) ruled that future
vows,
if they were given freely and consummated sexually, constituted an
indissoluable
marriage. Neither parental or kin-group consent, nor dowries, nor
publicity
were needed to complete a marital union.

At the same time, however,
canon law also insisted that marriages should
be
public and that parents should have a say in their creation. In
addition
to banning marriage within the fourth degree of consanguinity, the
Fourth
Lateran Council had also banned marriages concluded in secrecy. The
Council's
intent had been to provide an effective means of enforcing
consanguinity
laws: by making marriage public, incest impediments might come to light
more readily. The Council also intended to counteract a series of
problems that had arisen from a definition of marriage based on consent
and sex. In a court of law, for example, it was difficult to prove or
disprove
whether the parties to a marriage had exchanged vows consensually or
had
consummated the union freely. Public marriage had placing the consent
of
both parties on display and reinforcing it with the testimony of
witnesses.
Also, secret marriages had the potential to invalidate subsequent,
public
marriages and this, in turn, threatened the social functions of
marriage
as a tool of alliance-making and property transfer. As James A.
Brundage
notes,

The
upper classes sought to make their marriages
as public and as splendid as possible, not only as a matter of honor
and
social obligation, but also to assure that property transactions
connected
with the marriage would be honored.

From 1215 on, therefore,
canon law on marriage formed between the sometimes
contradictory requirements of consent and publicity, which may explain
the hesitance of theologians to affirm the sacramentality of marriage
unequivocally.
Albert the Great (c. 1200-1280) allowed it, but only because the
sacrament
helped married people achieve the goals of marriage (Brundage, 432).
Duns
Scotus (1270-1308) solved the problem by distinguishing two types of
marriage:
by itself, free mutual consent created a valid marriage, but only
a public, church ceremony could establish a sacramental marriage.
Others absorbed sacramentality into Gratian's two stages of marriage,
initiation
and completion. According to this view, a couple received one portion
of
the sacramental grace that marriage conferred in the first stage, when
they exchanged vows; they received the second portion, so to speak,
when
they consummated the union sexually. The view which ultimately
prevailed,
however, was that of Thomas Aquinas, who affirmed that marriage was a
sacrament
and that the exchange of consent itself conferred grace (Brundage,
433).
In 1215, the Fourth
Lateran Council made
the following rulings on incest and clandestine
marriage:

§50. On the
Restriction of Prohibitions to Matrimony
It should not be judged reprehensible if human decrees are sometimes
changed according to changing circumstances, especially when urgent
necessity
or evident advantage demands it, since God himself changed in the new
Testament
some of the things which he had commanded in the old Testament. Since
the
prohibitions against contracting marriage in the second and third
degree
of affinity, and against uniting the offspring of a second marriage
with
the kindred of the first husband, often lead to difficulty and
sometimes
endanger souls, we therefore, in order that when the prohibition ceases
the effect may also cease, revoke with the approval of this sacred
council
the constitutions published on this subject and we decree, by this
present
constitution, that henceforth contracting parties connected in these
ways
may freely be joined together. Moreover the
prohibition
against marriage shall not in future go beyond the fourth degree of
consanguinity
and of affinity, since the prohibition cannot now generally be
observed
to further degrees without grave harm. The number four agrees well with
the prohibition concerning bodily union about which the Apostle says,
that
the husband does not rule over his body, but the wife does; and the
wife
does not rule over her body, but the husband does; for there are four
humors
in the body, which is composed of the four elements. Although the
prohibition
of marriage is now restricted to the fourth degree, we wish the
prohibition
to be perpetual, notwithstanding earlier decrees on this subject issued
either by others or by us. If any persons dare to marry contrary to
this
prohibition, they shall not be protected by length of years, since the
passage of time does not diminish sin but increases it, and the longer
that faults hold the unfortunate soul in bondage the graver they are.

§51. Prohibition
of Clandestine Marriages
Since the prohibition against marriage in the three remotest degrees
has been revoked, we wish it to be strictly observed in the other
degrees.
Following in the
footsteps of our predecessors, we altogether
forbid clandestine marriages and we forbid any priest to presume
to be present at such a marriage. Extending the special custom of
certain regions to other regions generally, we decree
that when marriages are to be contracted they
shall
be publicly announced in the churchesby priests, with a suitable time being fixed
beforehand within which whoever wishes and is able to may adduce a
lawful
impediment. The priests themselves shall
also investigate whether there is any impediment. When there appears
a credible reason why the marriage should not be contracted, the
contract
shall be expressly
forbidden until there has been established from clear documents what
ought to be done in the matter. If any persons presume to enter into
clandestine
marriages of
this kind, or forbidden marriages within a prohibited degree, even
if done in ignorance, the offspring of the union shall be deemed
illegitimate
and shall have no help
from their parents' ignorance, since the parents in contracting the
marriage could be considered as not devoid of knowledge, or even as
affecters
of ignorance.
Likewise the offspring shall be deemed illegitimate if both parents
know of a legitimate impediment and yet dare to contract a marriage in
the presence of the
church, contrary to every prohibition. Moreover the parish priest who
refuses to forbid such unions, or even any member of the regular clergy
who dares to attend
them, shall be suspended from office for three years and shall be
punished
even more severely if the nature of the fault requires it. Those who
presume
to be united
in this way, even if it is within a permitted degree, are to be given
a suitable penance. Anybody who maliciously proposes an impediment, to
prevent a legitimate
marriage, will not escape the church's vengeance. (emphasis
added)